1. Field of the Invention
The present invention relates to electro-optic modulator arrays, e.g. arrays comprising PLZT (lanthanum substituted lead titanite zirconate) pixel portions that are addressable electrically for use in light valve devices, and more particularly to improved fabrication methods for, and constructions of, such arrays.
2. Background Art
U.S. Pat. No. 4,406,521 describes an imaging apparatus empolying light valve devices of the class referred to above. In general, light valve devices of this kind employ an electroded PLZT modulator panel sandwiched between crossed polarizers and the panel is activated to operate in a quadratic Kerr cell mode. The modulator panel comprises a plurality of electrodes formed on one major surface in a manner allowing selective application of discrete electric fields across respective pixel portions of the panel. When the field is present across a particular pixel portion, it becomes birefringent and the polarization of light passing therethrough from the ingress polarizer is changed so as to pass through the egress polarizer. When a field is absent the modulator material remains isotropic so that egressing light is blocked by the egress polarizer.
U.S. Pat. Nos. 3,873,187; 4,569,573 and 4,491,393 describe modulators (for use in light valve devices) in which the addressing electrode structure is fabricated so as to extend along the direction of light passage through the modulator material. In this manner such an "in-depth" electrode approach provides a transverse electric field that is more uniform and that is effective throughout a large portion of light passage dimension of the modulator. In addition, the in-depth electrode approach allows use of lower electric fields, which has advantages in driver design and increases device longevity. One problem connected with the in-depth electrode approach is that modulator fabrication is extremely difficult, e.g. from the viewpoints of accurately and reliably forming the addressing electrodes and making electrical contacts to the addressing electrodes.
U.S. Pat. No. 4,707,081 describes a highly useful modulator fabrication which employs: (i) photoresist masking of a linear pixel region of a modulator wafer, (ii) grooving the wafer along each edge of the strip, (iii) vacuum deposition of metal on the wafer including the grooves and photoresist mask and (iv) further grooving and mask removal to define separately electroded modulator pixels with contact leads.
While the technique of the above-noted application is very advantageous, there are certain modulator embodiments wherein the definition of the modulator into pixels by grooving has disadvantages. For example, where high resolutions are desired, the grooving approach has limitation because the material is fragile. Also, the grooving approach to pixel definition is tedious and time consuming.